/*
 * A JavaScript implementation of the SHA256 hash function.
 *
 * FILE:	sha256.js
 * VERSION:	0.8
 * AUTHOR:	Christoph Bichlmeier <informatik@zombiearena.de>
 *
 * NOTE: This version is not tested thoroughly!
 *
 * Copyright (c) 2003, Christoph Bichlmeier
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holder nor the names of contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * ======================================================================
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ''AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/* SHA256 logical functions */
function rotateRight(n, x) {
  return (x >>> n) | (x << (32 - n));
}
function choice(x, y, z) {
  return (x & y) ^ (~x & z);
}
function majority(x, y, z) {
  return (x & y) ^ (x & z) ^ (y & z);
}
function sha256_Sigma0(x) {
  return rotateRight(2, x) ^ rotateRight(13, x) ^ rotateRight(22, x);
}
function sha256_Sigma1(x) {
  return rotateRight(6, x) ^ rotateRight(11, x) ^ rotateRight(25, x);
}
function sha256_sigma0(x) {
  return rotateRight(7, x) ^ rotateRight(18, x) ^ (x >>> 3);
}
function sha256_sigma1(x) {
  return rotateRight(17, x) ^ rotateRight(19, x) ^ (x >>> 10);
}
function sha256_expand(W, j) {
  return (W[j & 0x0f] +=
    sha256_sigma1(W[(j + 14) & 0x0f]) +
    W[(j + 9) & 0x0f] +
    sha256_sigma0(W[(j + 1) & 0x0f]));
}

/* Hash constant words K: */
let K256 = [
  0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1,
  0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
  0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786,
  0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
  0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
  0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
  0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b,
  0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
  0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a,
  0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
  0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
];

/* global arrays */
let ihash, count, buffer;
let sha256_hex_digits = "0123456789abcdef";

/* Add 32-bit integers with 16-bit operations (bug in some JS-interpreters:
 overflow) */
function safe_add(x, y) {
  let lsw = (x & 0xffff) + (y & 0xffff);
  let msw = (x >> 16) + (y >> 16) + (lsw >> 16);
  return (msw << 16) | (lsw & 0xffff);
}

/* Initialise the SHA256 computation */
function sha256_init() {
  ihash = Array.from({ length: 8 });
  count = Array.from({ length: 2 });
  buffer = Array.from({ length: 64 });
  count[0] = count[1] = 0;
  ihash[0] = 0x6a09e667;
  ihash[1] = 0xbb67ae85;
  ihash[2] = 0x3c6ef372;
  ihash[3] = 0xa54ff53a;
  ihash[4] = 0x510e527f;
  ihash[5] = 0x9b05688c;
  ihash[6] = 0x1f83d9ab;
  ihash[7] = 0x5be0cd19;
}

/* Transform a 512-bit message block */
function sha256_transform() {
  let a, b, c, d, e, f, g, h, T1, T2;
  let W = Array.from({ length: 16 });

  /* Initialize registers with the previous intermediate value */
  a = ihash[0];
  b = ihash[1];
  c = ihash[2];
  d = ihash[3];
  e = ihash[4];
  f = ihash[5];
  g = ihash[6];
  h = ihash[7];

  /* make 32-bit words */
  for (let i = 0; i < 16; i++) {
    W[i] =
      buffer[(i << 2) + 3] |
      (buffer[(i << 2) + 2] << 8) |
      (buffer[(i << 2) + 1] << 16) |
      (buffer[i << 2] << 24);
  }

  for (let j = 0; j < 64; j++) {
    T1 = h + sha256_Sigma1(e) + choice(e, f, g) + K256[j];
    if (j < 16) T1 += W[j];
    else T1 += sha256_expand(W, j);
    T2 = sha256_Sigma0(a) + majority(a, b, c);
    h = g;
    g = f;
    f = e;
    e = safe_add(d, T1);
    d = c;
    c = b;
    b = a;
    a = safe_add(T1, T2);
  }

  /* Compute the current intermediate hash value */
  ihash[0] += a;
  ihash[1] += b;
  ihash[2] += c;
  ihash[3] += d;
  ihash[4] += e;
  ihash[5] += f;
  ihash[6] += g;
  ihash[7] += h;
}

/* Read the next chunk of data and update the SHA256 computation */
function sha256_update(data, inputLen) {
  let i;
  let index;
  let curpos = 0;
  /* Compute number of bytes mod 64 */
  index = (count[0] >> 3) & 0x3f;
  let remainder = inputLen & 0x3f;

  /* Update number of bits */
  if ((count[0] += inputLen << 3) < inputLen << 3) count[1]++;
  count[1] += inputLen >> 29;

  /* Transform as many times as possible */
  for (i = 0; i + 63 < inputLen; i += 64) {
    for (var j = index; j < 64; j++) buffer[j] = data.charCodeAt(curpos++);
    sha256_transform();
    index = 0;
  }

  /* Buffer remaining input */
  for (var j = 0; j < remainder; j++) buffer[j] = data.charCodeAt(curpos++);
}

/* Finish the computation by operations such as padding */
function sha256_final() {
  let index = (count[0] >> 3) & 0x3f;
  buffer[index++] = 0x80;
  if (index <= 56) {
    for (var i = index; i < 56; i++) buffer[i] = 0;
  } else {
    for (var i = index; i < 64; i++) buffer[i] = 0;
    sha256_transform();
    for (var i = 0; i < 56; i++) buffer[i] = 0;
  }
  buffer[56] = (count[1] >>> 24) & 0xff;
  buffer[57] = (count[1] >>> 16) & 0xff;
  buffer[58] = (count[1] >>> 8) & 0xff;
  buffer[59] = count[1] & 0xff;
  buffer[60] = (count[0] >>> 24) & 0xff;
  buffer[61] = (count[0] >>> 16) & 0xff;
  buffer[62] = (count[0] >>> 8) & 0xff;
  buffer[63] = count[0] & 0xff;
  sha256_transform();
}

/* Split the internal hash values into an array of bytes */
function sha256_encode_bytes() {
  let j = 0;
  let output = Array.from({ length: 32 });
  for (let i = 0; i < 8; i++) {
    output[j++] = (ihash[i] >>> 24) & 0xff;
    output[j++] = (ihash[i] >>> 16) & 0xff;
    output[j++] = (ihash[i] >>> 8) & 0xff;
    output[j++] = ihash[i] & 0xff;
  }
  return output;
}

/* Get the internal hash as a hex string */
function sha256_encode_hex() {
  let output = new String();
  for (let i = 0; i < 8; i++) {
    for (let j = 28; j >= 0; j -= 4)
      output += sha256_hex_digits.charAt((ihash[i] >>> j) & 0x0f);
  }
  return output;
}

/* Main function: returns a hex string representing the SHA256 value of the
 given data */
function sha256_digest(data) {
  sha256_init();
  sha256_update(data, data.length);
  sha256_final();
  return sha256_encode_hex();
}

/* test if the JS-interpreter is working properly */
function sha256_self_test() {
  return (
    sha256_digest("message digest") ==
    "f7846f55cf23e14eebeab5b4e1550cad5b509e3348fbc4efa3a1413d393cb650"
  );
}

/* 360OS export function */
export default {
  sha256_digest,
};
